Reasons not to use Eventbrite.com (or Meetup.com)

All of this applies to meetup.com as well as
eventbrite.com

There are two things wrong with eventbrite.com. The superficial flaw
is that it requires running nonfree Javascript code. That's
superficial in the sense that it could be fixed easily, but it's a
fatal flaw until they do fix it; people should not run that nonfree
Javascript code.
See The
Javascript Trap.

The fundamental flaw is that using eventbrite to register people for an
event collects data about them and gives it to a company (with big
brother reading over its shoulder).

If you want to register attendees for an event, please do it the
ethical way: don't make them run any nonfree software, and don't make
them send personal data (not even to you). That's
how the FSF does it.